1. Field of the Invention
The present invention relates to a device for moving a nozzle on a wire cutting electric discharge machine in the vertical direction, and more particularly to a nozzle elevating device for a wire cuttng electric discharge machine wherein the nozzle can automatically adhere to the upper surface of the workpiece being processed, and when the nozzle is about to strike an obstacle while it is being lowered, the device will automatically stop the descent of the nozzle.
2. Description of the Related Art
Generally, a wire cutting electric discharge machine is provided with a worktable on which the workpiece being processed is removably supported, and which can be freely moved horizontally in the direction of the X and Y axes, and in addition, is provided with a wire electrode guide which guides a wire elctrode which travels in the vertical direction and perforates the workpiece. It is desirable that this wire electrode guide approach as close as possible to the surface of the workpiece so that, generally, a process liquid or dielectric fluid is introduced through a nozzle into the discharge section between the workpiece and the wire electrode.
In a wire cutting electric discharge machine, in order to carry out efficiently the removal of the scrap from the electric discharge position, and the cooling of the position of the electric discharge processing of the workpiece, and to prevent scattering of the process liquid, it is desirable that the nozzle adhere to the surface of the workpiece. Accordingly, conventionally, a manual operation is adopted to move the nozzle in the vertical direction, or a semi-automatic operation is adopted by driving a motor to effect vertical movement of the nozzle.
However, manual operation can be extremely troublesome. Also, in the case of operation by driving a motor, it is troublesome that the motor must be halted while watching the nozzle approaching the surface of the workpiece. In addition, there is extreme variation in the adherability of the workpiece and the nozzle. Occasionally, the nozzle presses too strongly against the surface of the workpiece.